This invention relates to a front end loader of the type having a material handling bucket supported for pivotal movement about a transverse axis by the forward end of a boom structure. In machines of this type, usually some form of hydraulic means is provided for tilting the bucket about its pivotal connection with the boom structure to cause the bucket to be located with its cutting edge in engagement with the ground when in a dig position and rolled back for maintaining the material within the bucket when being transported to a dumping location. Thus, the present invention is directed to a control mechanism for automatically positioning the material handling bucket relative to the supporting boom structure during raising and lowering of the boom structure.
The conventional front end loader disclosed herein includes an elongated body having an engine compartment adjacent the rear end thereof and an operator's compartment mounted on the body. A pair of stanchions or uprights are fixedly secured to the body adjacent the opposite sides of the engine compartment and extend upwardly therefrom. A pair of lift arms are pivotally connected at one end about a common pivot axis on the respective uprights and extend generally forwardly along opposite sides of the body in close proximity to the operator's compartment and terminate in downwardly directed end portions. A material handling device, such as a bucket, is pivotally supported on the free ends thereof and is normally pivoted between "roll-back" and "dump" positions by hydraulically operated linkage mechanism that is controlled by the operator seated in the operator's compartment.
The pivotal movement of the bucket is accomplished through a pair of fluid rams, each one having one end pivotally connected to the bucket at a location spaced from the pivotal connection of the bucket to the free ends of the lift arms and an opposite end connected to a lift arm at a location laterally offset from the longitudinal axis of the downwardly directed end portion of the lift arm.
In the raising and lowering of the lift arms and the bucket relative to the uprights, normally through a second pair of fluid rams located between the uprights and the lift arms or boom structure, the tilt of the bucket tends to increase and, if uncorrected, might dump material over the top edge of the bucket and down onto the tractor. To correct this tendency, it is customary to incorporate a self-leveling linkage system that cooperates with the tilt fluid ram for pivoting the bucket so that the attitude of the bucket remains substantially constant as the lift arms are raised after the bucket has been filled with material.
While the compensating systems of the prior art have contributed significantly to overcoming the problem of dumping material or contents from the material handling device onto the tractor, the arrangements disclosed have been relatively complex and expensive to fabricate. Thus, it is an object of the present invention to provide an improved bucket leveling mechanism that is easy to manufacture and reliable in operation in various environments.